Rumors that Paul McCartney will join Brian Wilson onstage in London next month have started to spread after a source reportedly told U.K. paper The Daily Express of the upcoming duet. “Paul and Brian are good mates and as Brian is going to be performing from Pepper, the word is Paul will join him onstage one night for a couple of songs,” the insider claims.

Though the pair were chart rivals forty years ago, if rumor becomes reality McCartney will join Wilson at one of his six scheduled nights at the Royal Festival Hall in September — as the source indicates, to guest on a track from Sgt. Pepper’s Lonely Hearts Club Band, an album the Beatles have long said was greatly influenced by the Beach Boys’ Pet Sounds.

McCartney and Wilson have paired up in the past, for a duet on Wilson’s 2004 album Gettin’ In Over My Head and at a 2002 fundraiser for Open Hearts, Clear Minds, a charity started by McCartney’s soon-to-be ex-wife Heather Mills. McCartney also introduced Wilson when the Beach Boy was inducted into the Songwriters’ Hall of Fame in 2007, saying, “So thank you, sir, for everything you’ve done for me, for making me cry, for having that ‘thing’ you can do with your music. You just put those notes and those harmonies together, stick a couple of words over the top of it and you’ve got me. Any day.”